Chapter 8

Compare and contrast how C4 and CAM plants avoid photo respiration and conserve water.

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Describe the general structure of chloroplasts.

Outer membrane Inner membrane Inner membrane space Stroma Granum Thylakoid Thylakoid lumen

Outline the three phases of the Calvin cycle.

Phase 1 Carbon fixation CO2 is incoorperated into an organic molecule via rubisco Phase 2 Reduction and carbohydrate production ATP is used as a source of energy and NADPH donates high energy electrons Phase 3 regeneration of RuBP two G3P are used to make glucose and other sugars the remaining 10 G3P are needed to regnerate RuBP via several enzymes. ATP is required for RuBP to be regenerated.

Explain the concept of photorespiration.

The metabolic process occuring in C3 plants that occurs when the enzyme rubisco combines with O2 instead of CO2 and produces only one molecule of 3PG instead of 2 thereby reducing photosynthetic efficientcy

Explain how O2 is produced by photosystem II.

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Describe the incoming components and the net product(s)

the Calvin cycle begins by using carbon from an inorganic source, that is, CO2, and ends with organic molecules that will be used by the plant to make other molecules.

Diagram the path of electron flow through photosystem II.

High energy electron usually by resonance energy transfer, this high-energy electron then moves to the primary electron acceptor, which is a chlorophyll molecule lacking Mg2+, called pheophytin (Pp). Pheophytin is permanently bound to photosystem II and transfers the electron to a plastoquinone molecule, designated QA, which is also permanently bound to photosystem II. Next, the electron is transferred to another plastoquinone molecule designated QB, which can accept two high-energy electrons and bind two H+. As shown earlier in Figure 8.8, QB can diffuse away from the reaction center. Low energy electrons, 2 water molecule bind to the manganese cluster D1 catalyse the removal of four low energy electrons from H2O molecules to produce O2 and H+. Each low energy electron is transferred one at a time to an mino acid in D1 and then to P680+ to produce P680

Write the general equations that represent the process of photosynthesis.

CO2 +2H2A+ Lght energy--> Ch2O + A2 + h20 In green plants A becomes oxygen so : Co2+ 2H2O+ Light energy --> CH2O + O2 + H2O when carb produced is glucose multiply everything by 76 6CO2+ 12H2O + Light energy--> C6H12O6+ 6O2+6H2O

Describe how the light-harvesting complex absorbs light energy and how it is transferred via resonance energy transfer.

It is composed of several dozen pigment molecules that are anchored to trans-membrane proteins. The role of the complex is to directly absorb photons of light. When a pigment molecule absorbs a photon, an electron is boosted to a higher energy level. As shown in Figure 8.11, the energy (not the electron itself) is transferred to adjacent pigment molecules by a process called resonance energy transfer.

Describe how pigments absorb light energy and the types of pigments found in plants and green algae.

When light strikes a pigment, some of the wavelengths of light energy are absorbed, while others are reflected. For example, leaves look green to us because they reflect radiant energy of the green wavelength

Explain the process of cyclic photophosphorylation in which only ATP is made.

When light strikes photosystem I electrons are excited and sent to ferredoxin (Fd), the electrons are then transferred to Qb, to the cytochrome complex, then to plastocyanin (Pc) and back to photosystem I this produces an H+ electrochemical gradient which is used to make ATP via ATP synthase.

Explain how photosynthesis powers the biosphere.

The existence of most species relies on a key energy cycle that involves the interplay between organic molecules (such as glucose) and inorganic molecules, namely, O2, CO2, and H2O Photoautotrophs make a large proportion of the Earth's organic molecules via photosynthesis

Outline the steps in which photosystem II and I capture light energy and produce O2, ATP, and NADPH.

1a. light excites the electrons within pigment molecules in the light harvesting complex of PSII, the excited electrons move down an ETC to more electron negative atoms producing an H+ electrochemical gradient. 1b. electrons are removed from water and transferred to a pigment called p680, this process creates O2 and produces additional H+ in the lumen. 2. electrons eventually reach PSI where a second input of light boost them to a very high energy level. 3. Two high energy electrons plus an H+ are transferred to NAD+ to make NADPH. This removes some H+ from the stroma 4. The production of O2, the pumping of H+ across the thylakoid membrane and the synthesis of NADPH all contribute to the production of an H+ electrochemical gradient, this gradient is used to make ATP via ATP synthase

Define the general properties of light.

Light is essential to support life on Earth. Light is a type of electromagnetic radiation, so named because it consists of energy in the form of electric and magnetic fields. Light also has properties of particles, Albert Einstein formulated the photon theory in which he discovered that light is composed of discrete particles called photons

Compare and contrast the two phases of photosynthesis: the light reactions and carbon fixation.

The light reactions, through which ATP, NADPH, and O2 are made, occur at the thylakoid membrane. The Calvin cycle, in which enzymes use ATP and NADPH to incorporate CO2 into carbohydrate, occurs in the stroma